华北平原古河道地裂缝的成因机理探讨

发布时间：2018-10-05 17:49

【摘要】：华北平原为古河流发育比较广泛的地区,曾分布有黄河、漳河、潮白河等众多河流,区内构造断裂和次级块体分布纵横,构造活动及次级块体的隆起与下降使古河床不断的抬升、沉降从而导致古河流发生改道,继而造成了华北平原丰富的古河道地层地貌。古河道是地裂缝发生的依附载体,由于其特殊的地层性质、形状及埋深产生出一种非构造裂缝,称之为古河道地裂缝。本文以大名县的地裂缝为例,对古河道地裂缝的成因机理进行研究讨论,不仅丰富完善了华北平原地裂缝的成因机理,也为防灾减灾提供理论依据。本文通过查阅和搜集相关的地质资料,查明了华北平原浅埋古河道的分布规律、地层岩性特征、地质构造等地质环境背景。以大名县的地裂缝为典型研究案例,通过野外地质调查,基本查明了古河道地裂缝的分布特征;以钻探和槽探为技术手段,揭示了古河道地裂缝的剖面结构特征,在此基础上初步分析探讨了古河道地裂缝的影响因素及成因模式。最后通过数值模拟研究,探讨和分析了抽水作用下古河道上覆土层的埋深及初始地下水位对地裂缝形成的影响,总结了抽水作用下古河道地裂缝的发育规律及成因机理。取得的主要研究成果如下:(1)通过查阅和搜集华北平原相关的地质资料,分析了华北平原古河道所处的地质构造活动以及地质地貌环境背景,并说明了古河道的地层特征及发育规律,为地裂缝的产生提供了良好的依附先存条件。(2)通过对华北平原进行野外地质调查,根据现有的地裂缝调查资料,结合古河道及地裂缝的发育情况,绘制了华北平原古河道地裂缝分布图。(3)以大名县的地裂缝为例,根据探槽和钻探的剖面特征,并结合地裂缝的展布情况及地层的发育规律,分析了古河道地裂缝的平面及剖面特征。(4)在对比分析地裂缝的发生与抽水、地震和降雨的时空相关性的基础上,结合古河道的特殊地质特征,探讨了古河道地裂缝形成的三种成因模式,其中抽水形成的地层差异沉降为主要成因方式。(5)通过对抽水引发古河道产生差异沉降形成的地裂缝模式进行数值模拟,分析了抽水作用下古河道形成地裂缝的发育特征、成因机理,并探讨了古河道埋深、地下初始水位对地裂缝形成的影响。
[Abstract]:The North China Plain is an area where ancient rivers developed widely. There were many rivers, such as the Yellow River, the Zhangzhou River, the Chaobai River, and so on. The tectonic faults and secondary blocks were distributed vertically and horizontally in the area. Tectonic activity and the uplift and descent of secondary blocks make the paleo-river bed uplift and subsidence lead to the diversion of ancient rivers, which leads to the rich paleochannel stratigraphic landforms in the North China Plain. The paleochannel is the dependent carrier of the occurrence of ground fissure. Because of its special stratigraphic property, shape and buried depth, it produces a kind of non-structural fracture, which is called the ancient river channel ground fracture. Taking the ground fissures in Daming County as an example, this paper studies and discusses the formation mechanism of the ground cracks in ancient rivers, which not only enriches and perfects the formation mechanism of the ground cracks in the North China Plain, but also provides a theoretical basis for disaster prevention and mitigation. By consulting and collecting relevant geological data, this paper finds out the geological environment background of shallow buried paleochannel in North China Plain, such as distribution law, stratigraphic lithologic characteristics, geological structure and so on. Taking the ground fissures in Daming County as a typical case, the distribution characteristics of the ground fractures in ancient rivers are basically ascertained through field geological investigation, and the profile structural characteristics of the ground fractures in ancient rivers are revealed by drilling and trench exploration as technical means. On the basis of this, the influencing factors and the cause of formation of the ancient channel ground fissures are preliminarily analyzed and discussed. Finally, through numerical simulation, the influence of the buried depth of the overlying layer and the initial groundwater level on the formation of the ground fissure in the ancient river course under the action of pumping water is discussed and analyzed, and the law of the development and the formation mechanism of the ground crack in the ancient river course under the action of pumping water are summarized. The main research results are as follows: (1) by consulting and collecting relevant geological data of North China Plain, the geological tectonic activities and geological and geomorphological environment background of paleochannel in North China Plain are analyzed. The stratigraphic characteristics and development law of paleochannel are explained, which provides a good precondition for the occurrence of ground fissure. (2) through the field geological survey of North China Plain, according to the existing ground fracture investigation data, Combined with the development of paleochannel and ground fissures, the distribution map of ground fissures along ancient rivers in North China Plain is drawn. (3) taking the ground fissures in Daming County as an example, according to the profile characteristics of exploration channels and drilling, and combining with the distribution of ground fractures and the rules of formation development, The plane and profile characteristics of the paleochannel ground fissure are analyzed. (4) on the basis of the correlation between the occurrence of the ground fissure and the time and space correlation of pumping water, earthquake and rainfall, the special geological characteristics of the paleochannel are combined. In this paper, three genetic models of the formation of ancient channel ground fissures are discussed, among which the formation differential settlement caused by pumping water is the main cause of formation. (5) through numerical simulation of the ground fissure model caused by pumping ancient river channel, the formation of ground fissure caused by the differential settlement of ancient river course is simulated. In this paper, the characteristics and mechanism of formation of ground fissure in ancient river course under pumping action are analyzed, and the influence of buried depth and initial groundwater level on the formation of ground fissure is discussed.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P642.2

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